Bugman wrote:
...I prefer the 90% alcohol because it seeps into the tiny spaces between the posts and makes it to the actual contact pretty easily. A contact / TV tuner cleaner might work OK if you could get it inside. I like 90% also because I know it evaporates with no trace very quickly. WD-40 cleans contacts too, but that is known to leave a lubricating residue with is probalby not best for this application either. I've fixed double characters, and no key response this way on many keyboards. Might be worth a try if it doesn't inprove on its own.
TV tuner/contact cleaner is especially made with low surface tension so that it penetrates even the tiniest clearances to reach the contacts. The same is true for potentiometer cleaning solutions. The point of all of them is to dissolve soil (and contact cleaners can also dissolve some oxides) and leave a thin protective film to delay future oxidation. Lubricants are usually included. Any of them work best with repeated operation (friction) of the contacts while drying, to help abrade soil and oxides. This is also true of "noisy" pots, which must be oscillated repeatedly from stop to stop while the cleaner is still wet and evaporating to clear the wiper contact and its "track" on the element and keep it clear as the solvent evaporates. Switch contacts benefit from the same repeated operation, for the same reason. In fact, many dirty contacts (and pots) can be "cleaned" just by rapid repeated operation--hundreds of times in some cases. The self-cleaning action of good contact design clears the soil and oxide and restores proper operation. Regular use maintains it. -michael NadaNet and AppleCrate II: parallel computing for Apple II computers! Home page: http://home.comcast.net/~mjmahon "The wastebasket is our most important design tool--and it's seriously underused."